Adguard home add-on static DNS server question

Hi
I just installed the adguard home add-on to my hassio instance running on a Rpi4. Step 1 of the setup describes setting up a static IP and static external DNS servers. I decided to do this using nmcli command directly on the pi using an attached monitor and keyboard. The DNS servers are shown to be Google DNS (8.8.8.8 and 8.8.4.4) in the linked instructions (operating-system/network.md at bdc990911786cd2dffdf53b1fc3e18966d92c122 · home-assistant/operating-system · GitHub) but further below it says to set the DNS server as the IP of your router. Which should i set this DNS server as? Thanks

Also another related question. My router is running Asus Merlin, do I point the DNS server on both LAN and WAN towards the hassio rpi4 or just the LAN?